This invention relates to a device for driving and guiding a rapier of a weaving machine, comprising a rotatable drive wheel provided for driving a rapier rod in a back and forth movement, and a guide channel formed by adjustable guide bodies in order to guide the said rapier rod according to a guide path in co-operation with the drive wheel. This invention further relates to a rapier weaving machine provided with at least one such drive and guide device.
A rapier weaving machine is equipped with one or more rapier systems, each rapier system comprising two cooperating rapiers. Each rapier system is provided for inserting a weft yarn into a shed formed between the warp yarns each time in successive inserting cycles. In each inserting cycle, the rapiers situated on either side of the shed are first moved towards one another in this shed, while the one rapier takes along a weft yarn. The rapiers meet in the middle of the shed and there the weft yarn taken along is taken over by another rapier. Finally, both rapiers are withdrawn from the shed back into their original positions.
For a good operation of such a rapier system, the two cooperating rapiers have to meet in a respective position (hereafter called “the take-over position”), making an impeccable take-over of the weft yarn possible. Furthermore, the movement path of the rapiers must be situated at the right height, almost in the plane of symmetry of the shed. With narrow weaving machines, the movement path of the rapiers must run parallel to the reed. With wide weaving machines, the rapier heads must lean against the reed in order to obtain a safe take-over of the weft yarn. For these reasons the known drive and guide devices for rapiers are provided with means, with which the movement paths of the rapier can be exactly adjusted.
Known rapiers primarily consist of a rapier rod with a built-in gear-rack, which carries a rapier head at its extremity that is provided with gripping means to take along a weft yarn. The rapier drive occurs by means of a drive gearwheel that acts on a gear-rack and is rotated in the one and the other sense of rotation alternatively in order to move the rapier into or out of the shed. In order to keep the rapier rod within reach of the drive gearwheel during this drive and to avoid lateral movements of the rapier rod, this rapier rod is guided in a U-shaped guide channel.
In the Belgian patent no 1 000 994 a drive and guide device for such a rapier is described, having a molded guide channel for the rapier rod, in which a series of guide rollers is provided opposite the drive gearwheel. The guide channel is connected, in a manner adjustable as to height, to the casing of the drive gearwheel, and this casing itself is likewise rotatable in order to be able to give the guide channel the exact orientation. These adjustments allow the take-over position of the rapier head to be adjusted in order to obtain an efficient take-over of the weft yarn. The guide rollers are mounted in a frame that is adjustable in a direction at right angles at the paths of movement in order to guide the rapier rods at the exact distance of the drive gearwheel. This device has the disadvantage that particularly much heat is developed, and that the rapier rods, especially at relatively high weaving speeds, are subject to premature wear.
In the Belgian patent no 1 004 622 such a drive and guide device is described, the U-shaped guide channel of which is formed between a profile with an L-shaped cross-section on the one side, and a guide ruler, hingedly attached and which can be moved back in order to open the guide channel at the front, on the other side. The guide ruler comprises only one guide roller near the point where the drive gearwheel acts on the gear-rack to absorb the radial force exerted by the gearwheel on the rapier rod. The guide ruler with the guide roller is adjustable in a horizontal direction at right angles on the direction of the path of movement. The L-section is supported by a carrier arm, which is adjustable in a horizontal direction.
In order to limit wear and development of heat to a minimum, it is important that the gear-rack is guided at the correct distance from the gearwheel. On the other hand, the rapier rod also is to be guided at the correct height, so that the gearwheel might act in the middle of the tooth space of the gear-rack. This to avoid that the teeth should rub against the sidewalls of the tooth spaces of the gear-rack. If both clearances (the horizontal and the vertical clearances) are not adjusted correctly, this might provoke premature wear of the gear-rack and an exaggerated heating of the rapier envelope, which will cause its rapid decline.
To adjust the horizontal clearance of the device according to the Belgian patent no 1 004 622 first the carrier arm to which the L-section is attached must be moved in the horizontal direction, and thereafter the hinged guide ruler with the guide roller must be adjusted again into the correct position in order to obtain a guide channel having the exact width. In order to be able to adjust the vertical clearance the L-sections can be adjusted as to height, but the hinged guide ruler must be adjusted separately on the side of the guide roller by inserting or removing thin shims between the hinge and the guide slat. The installation level of the drive gearwheels can also be adjusted step by step by means of shims. These adjustments of the vertical and horizontal clearances are difficult to perform and cannot be carried out with the required precision and moreover, they are particularly time-consuming and complicated.